Surgical microscopes provide a magnified view of the operating field to the surgeon. Ophthalmic surgical microscopes are commonly stereo zoom microscopes with binocular view ports for the surgeon, and frequently have one or two observer view ports at ninety degrees (left and right) to the surgeon. The working distance between the objective lens of the microscope and the surface of a patient eye may range from about 100 mm to about 200 mm. At this working distance, which provides a suitable field of access for the manual work of the surgeon, the field of view within a patient eye may be quite limited. It is quite common to then use an intermediate lens, such as the Binocular Indirect Ophthalmo Microscope (BIOM) of Oculus Optikgerat, to modify the magnification and field of view for the surgeon. This intermediate lens is mounted to the under-carriage of the microscope head, and includes mechanics to adjust focus, and to flip the lens into and out of the field of view of the microscope.
Other illumination or imaging devices may also be used in the surgical field. Ideally, all illumination and imaging sources would be directly integrated coaxial to and within the optical path of the operating microscope, without impacting the operating field for the surgeon, the observers, the anesthesiologists, and the like. This is not always possible. Without full integration as such, it is still desirable to provide a readily maneuverable mount for imaging and other accessories that is closely coupled to the surgical field, and the mechanical controls and attributes that are already integral to a well-functioning operating microscope.
A particular case of interest is the incorporation of optical coherence tomography (OCT) imaging into the surgical visualization practice. OCT provides high resolution imaging of ocular tissue microstructure, and is showing great promise to provide information to the surgeon that will improve therapeutic outcomes, and reduce the total economic burdens of surgery by reducing risk and reducing re-work. The current generation of OCT, known generally as Fourier Domain OCT, provides very fast volumetric images (>30 mega-voxels per second) at very high resolution (2.0 μm to 6.0 μm axial resolution, 10.0 μm to 20 μm lateral resolution) particularly well suited to visualizing the fine tissue layers and membranes that are often the subject of the surgical effort. In contrast to microscope visualization, OCT provides depth-resolved images, highlighting subsurface physiology and pathology, with full volumes over a 30 to 70 degree field of view acquired in about 1 to 3 seconds. However, the alignment requirements of OCT, particularly for retina imaging, but also for cornea imaging, may be quite demanding to obtain high quality images. A flexible, finely controlled, and stable imaging platform is desirable.
At present, there are no commercially available operating microscopes with integrated OCT capabilities. The Assignee of the present application has demonstrated handheld OCT imaging as discussed in, for example, U.S. Patent Application Publication No. 2007/0081166 entitled PORTABLE OPTICAL COHERENCE TOMOGRAPHY (OCT) DEVICES AND RELATED SYSTEMS; U.S. Patent Application Publication No. 2009/0268020 entitled OPTICAL COHERENCE TOMOGRAPHY (OCT) IMAGING SYSTEMS FOR USE IN PEDIATRIC OPHTHALMIC APPLICATIONS AND RELATED METHODS AND COMPUTER PROGRAM PRODUCTS; and U.S. Patent Application Publication No. 2009/0141237 entitled INTEGRATED OPTICAL COHERENCE IMAGING SYSTEMS FOR USE IN OPHTHALMIC APPLICATIONS AND RELATED METHODS AND COMPUTER PROGRAM PRODUCTS. Devices discussed therein are finding increasing utility in the operative field. However, in some embodiments, the handheld device may be relatively difficult to align and stabilize for imaging in the operating field.
Approaches have been established to address the stabilization issue. For example, one approach to stabilize a handheld probe is to use a simple planar mount coupled to the objective lens of the microscope. This device has a fixed armature length, and coarsely rotates around the lens. There are no height adjustments, and there is no ballast to control torque on the microscope head. Another approach has been adopted by Optovue. This approach uses an articulating arm attached to a structure other than the operating microscope. This approach lacks the fine control afforded by a well engineered operating microscope, and risks being obstructive to the broader operating field. A third approach has been to use an independent boom mount, with balance similar to an operating microscope, as illustrated in, for example, U.S. Pat. No. 8,064,989. This approach may add unnecessary bulk to the limited space of the operating theater.